my visa agent told me 20 days . I got my Non O visa for 90 days while she submitted for the retirement visa . Get multiple entry visa so you can go in and out of Thailand otherwise you will have to start the process all over again ......
I came on a tourist visa and was told I needed 20 days left in order to apply for the Non O Visa first . That was the first step then retirement visa . If it's too complicated have an agent help you . Probably you don't have enough time left ?